While the incidence of stroke is decreasing in this country, it is still a major cause of morbidity and mortality. Two significant risk factors for stroke, asymptomatic carotid atherosclerosis and nonvalvular atrial fibrillation, are each currently subjects of multicentered, prospective NIH studies. These studies are designed to evaluate the effectiveness of various practice styles currently utilized by physicians in this country. The proposed project, to be done in conjunction with the participating medical schools in the two NIH studies, will evaluate the relative benefit-cost/utility of the various options using the General Health Policy Model and Quality of Well-being questionnaire. to evaluate the relative cost-effectiveness, quality of life interviews will be conducted by phone on all consenting participants of both NIH studies. Financial data for the benefit-cost/utility analysis will be derived in part from the participating medical schools and in part from standardized national data. Health outcomes will come form the participating medical schools. Results will be quantitative analyses of the specific programs evaluated by the prospective studies. These results will help inform physicians in making treatment decisions by adding benefit-cost/utility information to the results of these two NIH studies. studies.